We will explore further the possibility that herpes simplex virus (HSV) modulates one or more cellular protein kinase families, either to promote efficient viral gene expression and DNA replication, or to prevent cellular responses that would inhibit efficient virus replication. As obligate intracellular parasites, viruses have profound effects on cellular proliferation, differentiation, and homeostasis. The machinery that regulates these states is often wholly or in part embodied in families of protein kinases and phosphatases that modulate the function of key effector proteins. These effector proteins are often transcription factors which induce gene expression required to sustain a particular phenotype, or to respond to extra-cellular signals, either trophic or stress-inducing. Establishment of primary herpesvirus infections on mucosal epithelium likely requires direct introduction of virus into the cycling cells of the basal cell layer, while reactivation of latent HSV occurs in post-mitotic neurons of dorsal root ganglia. Following anteriograde transport to the periphery, virus re-enters cells of the basal layer where additional rounds of replication results in ulcerative lesion development. In this portion of the Program Project Grant, we seek to extend our previous findings on the effects of HSV on the machinery that regulates cell cycle. Because the HSV replicative cycle occurs within cycling as well as postmitotic cells, we will manipulate the growth state of cell lines of both unlimited and limited life span. Specifically we will address questions about the role of virus infection on the activity of cyclin-dependent kinases (CDKs), the mechanisms of inhibition of CDKs, the viral gene products that contribute to regulation of CDKs, and the importance of regulating CDK activity for efficient virus replication. Armed with this information we can then experimentally address the importance of cell cycle regulation in the process of latency reactivation.